This is a proposal for a competitive renewal of a Pediatric General Clinical Research Center, including pediatric inpatient (8 beds) and ambulatory units, a neonatal scatterbed unit (2 beds), a core laboratory and research nutritionist. Approximately 90 research protocols cover investigations of normal infants, very low birth weight infants, infants who are small for gestational age, placentas (for studies of causes of birth defects and prematurity), cystic fibrosis, bronchopulmonary dysplasia, failure to thrive, inborn metabolic disease, chronic hepatic disease, coagulation defects, neutrophil disorders, sickle cell disease, polycystic kidney disease, fragile X syndrome, neurological (movement) disorders, diabetes mellitus, immunologic disorders, AIDS, chromosome disorders, bronchial asthma, behavioral disorders, cardiac disorders, vascular causes of central nervous system damage in the very low birth weight infant and endocrinopathies. Studies will range from the molecular biology of the pathogenesis of disease to carefully designed intervention studies. Numerous neonatal and pediatric protocols will employ a variety of stable isotopes in complex nutrition/metabolic studies including energy metabolism, substrate utilization and the metabolism and homeostasis of both organic and inorganic micronutrients.